01 - In a large mixing bowl, combine ground beef, breadcrumbs, milk, egg, chopped onion, minced garlic, Parmesan cheese, parsley, salt, and pepper. Gently fold until just incorporated, being careful not to overwork the meat.
02 - Roll the mixture into 1½-inch meatballs, yielding approximately 20 to 24 uniform pieces.
03 - For enhanced depth of flavor and texture, sear the meatballs in batches in a lightly oiled skillet over medium-high heat, turning every 2 to 3 minutes until golden on all sides.
04 - Arrange the meatballs in an even layer at the bottom of the crockpot.
05 - In a separate bowl, whisk together beef broth, cream of mushroom soup, Worcestershire sauce, soy sauce, dried thyme, onion powder, and garlic powder until smooth. Pour the gravy mixture evenly over the meatballs.
06 - Cover and cook on LOW for 4 to 5 hours or on HIGH for 2 to 3 hours, until the meatballs are cooked through and tender.
07 - Stir in the heavy cream. If the gravy is too thin, add the cornstarch slurry gradually while stirring, then cook on HIGH for an additional 10 to 15 minutes until thickened to your preference.
08 - Taste and adjust seasoning as needed. Serve hot over mashed potatoes, egg noodles, or steamed rice.